Just as a single reference. That tan-line on the lower right that starts switchbacking after the connection with the red-line. Thats the grey line running out to Nemuro on the lower right. You'll notice a lack of climbing up the East coast and a distinct lack of switchbacks.

Kaitei (海底) means "ocean bottom" in Japanese. Tappi-Kaitei and Yoshioka-Kaitei were two stations located within the Seikan Tunnel between the islands of Honshu and Hokkaido. They, together with Shiriuchi station, were closed to make way for construction of the Hokkaido Shinkansen high-speed train line.